Japanese Patent Application Laid-Open Publication No. 2002-134581 (Patent Document 1) mentions a reference wafer as a reference when microscopic asperities on the surface of a silicon wafer are measured, and discloses a technology of forming microscopic asperities on the surface by relative scanning of local etching when the reference wafer is manufactured. The document also discloses that NF3, CF4, or SF6, which is an active-species gas, is used in the local etching.
Japanese Patent Application Laid-Open Publication No. 2000-183017 (Patent Document 2 and corresponding U.S. Pat. No. 6,463,941) discloses a chemical-solution concentration control apparatus that controls the concentration of a chemical solution for use in wafer etching and cleaning and others, and discloses a mixed solution of ammonia and a hydrogen peroxide solution as an example of the chemical solution.
Japanese Patent Application Laid-Open Publication No. 10-172940 (Patent Document 3) discloses a silicon wafer cleaning apparatus that makes an adjustment so that the concentration of a chemical solution for use in silicon wafer cleaning is optimum, and discloses a mixed solution of ammonia and a hydrogen peroxide solution as an example of the chemical solution.
U.S. Pat. No. 6,830,943 (Patent Document 4) discloses a wafer including a calibration standard for semiconductor metrology, in which the wafer has a surface with a degree of roughness less than 1 Å and has a calibration layer formed of a metal oxide or the like on the surface of the wafer.